Known in the prior art is an aerating device (Booklet of Messrs "Schumascher Brandol area" GMBH and Co. KG, Germany) comprising a tubular air conduit with radial holes spaced along one of its side wall generatrices. Secured rigidly above each hole on the side wall of the air conduit is a dispersing member in the form of a cylinder plugged at both ends. The side surface of the cylinder facing the air conduit has air holes arranged coaxially with the radial holes and intended for the passage of air from the air conduit into the dispersing member. Each dispersing member is made from Brandol ceramics which are a mixture of pure natural quartz sand with artificial resin. The graininess of this ceramic material is 80-120 and the diameter of its pores, approximately 19.times.10.sup.-5 m.
The above-mentioned aerating device features a high aerating capability attributed to a high degree of dispersion of the air delivered into the aerated liquid. However, the design of said device denies the possibility of uniform distribution of air bubbles throughout the length of the air conduit owing to a discrete arrangement of the dispersing members on the side wall of the air conduit.
In addition, the provision of separate dispersing members and the sophisticated nature of their fastening to the air conduit as well as the use of costly materials for their manufacture increase the cost of the aerating device and the amount of labor involved in its installation.
A further known aerating device (SU, A1, 1803391) comprising a tubular air conduit whose external surface of its side wall is provided with longitudinal ribs alternating with longitudinal recesses. Each longitudinal recess in the side wall of the air conduit has radial holes. The external surface of the air conduit side wall is provided with a two-layer dispersing coating. The first (internal) layer of said coating is made of a fibrous material wound tightly on the external surface of the air conduit while the second (external) layer has the form of a continuous coating of a fibrous material.
The above-mentioned aerating device is of a simpler design than the preceding one.
However, there is no optimization of parameters of the aerating system in said device with respect to the delivery of air, loss of pressure, uniform distribution of air bubbles, service life of the device, etc. Therefore, in case of, for example, an insufficient density of layers of the dispersing coating, the degree of dispersion of the air delivered into the liquid being treated will be considerably reduced just as the uniformity of distribution of these bubbles in the zone of contact therewith, which means that the maximum amount of air delivered into the air conduit will enter said liquid at the initial portion of the air conduit, failing to reach its terminal portion.
An excess density of layers of the dispersing coating will increase considerably the expenditures of energy required for efficient aeration of liquid since the excess density increases considerably the resistance of the air conduit side wall to the passage of air into the aerated liquid and calls for a higher pressure in the air conduit to ensure the supply of the preset amount of air into the aerated liquid.